Tail seal greases for TBM

Protection of the wire brushes and tightness of the tail seal are essential in tunnel excavation. Tail sealants, thanks to their composition, are viscous, resistant to wash-out, and adhere to any damp surface.

Pumped continuously as the tunnel boring machine advances, CONDAT sealing compounds for tail seals allow for good filling of the interbrush chambers to:

• act as a barrier to water, mortar, and soil fines
• offer controlled consumption

Brushes thus protected by WR New Generation or SL 89 New Generation sealants show greater flexibility and greater durability. Injection of the tail seal greases takes place in 2 steps:

• at the start-up phase
• as the tunnel boring machine advances

Before starting to bore, it is imperative that a first filling of the brushes should be carried out.

The first-filling sealant WR 90 New Generation must be injected deep into the brushes until reflux on brush surfaces. All the brushes must be prepared in this way to ensure an uninterrupted sealing of the tail brushes . The consistency and adherence of the first-filling sealant ensures protection during the entire lifetime of the brushes.

As the tunnel boring machine advances, another seal grease is pumped continuously between the rows of brushes to complete the tightness of the tail seal: WR 89 New Generation. The latter ensures good filling of the chambers, extends the brushes' lifetime and it is perfectly compatible with the  WR 90 New Generation. Through its performance, it guarantees a good pressure control and therefore optimal safety for the personnel and the equipment.

For projects with lower constraints as regards profile and geology, CONDAT offers the sealant SL89 New Generation which provides protection of the brushes and good sealing (up to 2 bar).

The WR 89 NewGeneration and WR 90 NewGeneration  sealants have the following advantages:

• Biodegradability
• Respect of the environment in a spirit of sustainable development
• Self-extinguishing for added safety
• Resistance to wash-out
• Resistance to all types of grouting
• Compatible with emergency sealant
• Controlled consumption
• Adherence to all surfaces, even wet
• Uniform filling of the chambers
• Control of the confinement  → reduced risk of settlement
• Approved by TBM manufacturers

Following the high pressures that can compress and deform the brushes, an emergency sealant CONDAT EMERGENCY SEAL can be used to counter the arrival of water, grouting and soil fines.

This emergency sealant is injected in place of the usual sealant: same pump, same pipes and injection points. The emergency sealant, reacts in the presence of water, blocks any water ingress and creates a watertight barrier.

For more information about the products, their implementation, and a good match between the situation encountered and the solution to be considered, contact a CONDAT representative.